Conventionally, bearing apparatuses are used for the purpose of supporting a roll neck part, which is a shaft portion of a mill roll. In such bearing apparatuses, the mill roll is gradually worn while steel sheets are rolled, and therefore, it is necessary to frequently replace the mill roll. Accordingly, the bearing and the roll neck part are attached to each other with a predetermined fitting clearance between them, in a so-called loose fit manner. Thus, there has been a problem that a slippage occurs between an inner ring of the bearing and the roll neck part during operation of the mill roll, resulting in wear of the roll neck part having a lower hardness. In order to prevent this slippage, as shown in FIG. 5, a first key groove 62 is formed on one end face of an inner ring 61, and a second key groove 64 is formed on an outer peripheral face of a roll neck part 63. One end of a first key 65 is inserted into and locked to the first key groove 62, and an L-shaped other end of the first key 65 is inserted into and engaged with the second key groove 64. As a result, a relative slippage (called as “a creep”) between the inner ring 61 and the roll neck part 63 is prevented at one side of the inner ring 61, and wear of the roll neck part 63 having a lower hardness as compared with the inner ring 61 can be prevented (see, e.g., Patent Document 1).
In a conventional creep preventing rolling bearing apparatus 71, as shown in FIG. 6, by providing a cutout groove in a part of an inner ring 72 in an axial direction of a rolling bearing 76, there is formed a key groove 73 opened at an inner peripheral face 72i and at an outer peripheral face 72o of the inner ring 72. A second key groove 73′ is formed on an outer peripheral face 77o of a rotation shaft 77 along an axial direction f. By aligning the first key groove 73 and the second key groove 73′ and inserting a key 78, a creep between the inner ring 72 and the rotation shaft 77 is prevented (hereinafter, referred to as “an open type rolling bearing”).
In another conventional creep preventing rolling bearing apparatus 81, as shown in FIG. 7, intrusion of foreign matters from the exterior is prevented by providing a seal 89 for tight sealing on an outer side of a rolling bearing 86. To seal an internal space between an outer ring 85 and an inner ring 82 from outside the bearing, an outer peripheral face 89o of the seal 89 is fitted and fixed to an axial end portion of an inner peripheral face 85i of the outer ring 85, and a lip 89i of the seal 89 is arranged to be in sliding contact with an outer peripheral face 82o of the inner ring 82. To prevent the lip 89i of the seal 89 from contacting a first key groove 83 of the inner ring 82, the first key groove 83 is located axially inward of the inner ring 82 with respect to the seal 89, (hereinafter referred to as “a sealed rolling bearing”).